The hollow-Earth idea was first introduced by William Randa (John Goodman), a high-ranking official in Monarch, a clandestine organization that tracks the location of kaijus across the globe. In Skull Island, Monarch referred to them as massive unidentified terrestrial organisms -- or MUTOs for short. Anyway, Randa explained that the MUTOs live in enormous underground caverns all over the world. Several of these caverns lead to Skull Island, which is why so many of them call it home.

Now, a fake Monarch website set up to promote Godzilla: King of the Monsters goes even deeper into that theory. As Screen Rant points out, the website lets users track where Godzilla is heading in "real-time." After an appearance at San Diego Comic-Con in July, Godzilla swam west across the Pacific, eventually reaching the Marianas Trench before disappearing.

Godzilla eventually emerged west of Indonesia, where he started heading toward Antarctica, which is where King Ghidorah resides. The three-headed monster is being set up as the Big Bad in the upcoming King of the Monsters, hinting that Rodan and Mothra will have to team up with Godzilla to take him down.

So, how did Godzilla manage to stay off the radar for so long? Considering the Marianas Trench is the deepest known part of the ocean, it's plausible that Godzilla swam into it, then accessed one of the (possibly many) underground caverns, eventually resurfacing tens of thousands of miles away -- and on the other side of a major landmass.

Will we learn more about the Godzilla-verse's hollow-Earth theory and how the kaiju have been using it to navigate the planet? We won't know until Godzilla: King of the Monsters hits theaters on May 31 next year.